Isolated Hypothyroxinemia Does Not Affect Pregnancy

Adverse outcomes not elevated in women who develop condition during first half of pregnancy

THURSDAY, May 3 (HealthDay News) -- Women who develop isolated maternal hypothyroxinemia during the first half of pregnancy have no greater risk of adverse pregnancy outcomes than other women, researchers report in the May issue of Obstetrics & Gynecology.

Brian M. Casey, M.D., of the University of Texas Southwestern Medical Center at Dallas, and colleagues studied stored serum samples from 17,298 women who underwent thyroid-stimulating hormone screening during the first half of pregnancy. The investigators analyzed the samples for concentrations of free thyroxine and thyroid peroxidase antibodies, and identified isolated maternal hypothyroxinemia as a free thyroxine level below 0.86 ng/dL and a normal-range level of thyroid-stimulating hormone.

The researchers identified 233 cases (1.3 percent) of isolated maternal hypothyroxinemia. They found that pregnancy outcomes in these cases were no different than in women with normal levels of free thyroxine and thyroid-stimulating hormone.

"Thus, widespread prenatal screening for maternal thyroid disorders is not justifiable at this time," the authors conclude. "To further evaluate these issues, a randomized, placebo-controlled treatment trial to screen 120,000 pregnant women is being conducted by the Maternal-Fetal Medicine Units Network of the National Institute of Child Health and Human Development."

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